Copper-nickel-vanadium alloy



Jan. 16, 1968 $HRAMM 3,364,082

COPPER-NI CKEL- VANADIUM ALLOY Filed July 9, 1965 ALLOY4 I00 AZZC 46/06 EMFEQA wee, C.

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United States Patent 3,364,082 COPPER-NICKEL-VANADIUM ALLOY Jacob Schramrn, Cupsaw Lake, Ringwood, N.J., assignor to International Nickel Company, Inc., New York, N.Y., a corporation of Delaware Fiied July 9, 1965, Ser. No. 470,678 Claims. (Cl. 14812.7)

The present invention relates to copper-nickel alloys and, more particularly, to copper-nickel-vanadium alloys and products and to processes for increasing the strength and hardness thereof.

It is well known that copper-nickel alloys consisting essentially of copper and nickel in proportions nominally about seven parts copper and three parts nickel, referred to as 70:30 cupronickel alloys, have many advantageous characteristics including good weldability, ease of fabrication and good resistance to various kinds of corrosion, e.g., general corrosion, stress corrosion cracking, pitting corrosion, crevice corrosion, and fouling. These alloys have been successfully used for tubing and other articles in evaporators, condensers, distillation apparatus and other apparatus requiring good corrosion resistance, especially resistance to corrosion by seawater. However, the strength and hardness of commercially produced 70:30 cupronickel alloys in hot rolled or annealed conditions is undesirably low, e.g., 0.2% offset yield strength (yield strength) of about 17,000 pounds per square inch (p.s.i.) and ultimate tensile strength of about 50,000 p.s.i. or 55,000 p.s.i., and this low order of strength is unsatisfactory for many purposes. These alloys can be strengthened to a degree by cold working but the work hardening rate of the alloys is low and even when cold reduced about 50%, as by cold rolling or cold drawing, the yield strength thereof is only 75,000 to 80,000 p.s.i. and the tensile strength thereof is only modestly increased to about 80,000 p.s.i. to 85,000 p.s.i. It would be very difficult and very uneconomical to obtain further increases of the strength by more cold working. Moreover, there are many instances where the configuration and/or the intended use of the article to be produced, e.g., welded tubing, negates all practical possibility of producing the article as a whole in a cold worked condition characterized by even a modest level of strength or, if the article is to be exposed in use to even relatively low elevated temperatures, of retaining the benefits of cold work when the article is in use. Heretofore, there has been a need for high strength alloys having the specially good corrosion resistance and other advantages of 70:30 cupronickel alloys. Also, the art has been faced with problems of producing cupronickel alloys with improved strength by processes other than, or complementary to, cold working.

Although many attempts were made to overcome the foregoing difficulties and other disadvantages, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that a copper-nickel alloy having a special microstructure is characerized by improved yield strength of 45,000 p.s.i. to 130,000 p.s.i. or higher and improved ultimate tensile strength of 80,000 p.s.i. to 150,000 p.s.i. or higher and also by good corrosion resistance and ease of production.

It is an object of the present invention to provide a new high strength copper-nickel alloy having a special microstructure.

Another object of the invention is to provide a new process for producing copper-nickel alloys characterized by increased strengths and hardnesses.

The invention also contemplates a new copper-nickel alloy product produced by a new process.

It is another object of the invention to provide a coppernickel alloy of a new composition.

It is a further object of the invention to provide new copper-nickel alloy products including castings, tubing, rods, wires, sheet, strip, forgings, cold headed articles and other articles of manufacture characterized by advantageous combinatons of characteristics including improved high strength and hardness and good ductility up to relatively high temperatures, good general resistance to corrosive media such as seawater and ammonia-air-water atmospheres, good resistance to stress corrosion cracking, good weldability and ease of production.

The invention further contemplates a new cold-worked cooper-nickel alloy having a special chemical composition and microstructure and characterized by high yield strength of at least about 100,000 p.s.i., high ultimate tensile strength of at least about 120,000 p.s.i. and satisfactory ductility.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing in which the figure is a graph depicting relationships of Brinell hardness to aging temperature.

Generally speaking, the present invention contemplates a new precipitate strengthened copper-nickel-vanadium alloy which is of a special composition and which has a special microstructure comprising a face-centered-cubic copper-nickel matrix having therein a finely and evenly dispersed precipitate of a vanadium compound. The new precipitate strengthened alloy is characterized at room temperature by yield strength of at least about 45,000 p.s.i., ultimate tensile strength of at least about 80,000 p.s.i. and Brinell hardnesses of at least about Brinell hardness number (BHN), which are obtainable without cold working the alloy. Copper-nickel-vanadium alloys in accordance with the invention are of a special composition containing about 20% to about 40% nickel, 0.7% to about 2% vanadium and balance substantially copper. In addition, the special copper-nickel-vanadium alloy composition provided by the invention can contain up to about 1% silicon and/or up to about 2% aluminum provided that the sum of the percent silicon plus the percent of aluminum does not exceed 1% of the alloy and further provided that the total percentage of silicon plus aluminum plus vanadium does not: exceed 3% of the alloy. The invention also contemplates a new process for obtaining the special microstructure and other characteristics of the precipitate strengthened (precipitation hardened) alloy of the invention, which process comprises strengthening by an aging treatment at elevated temperature, whereby a copper-nickel-vanadium alloy of composition in accordance with the invention and having vanadium in supersaturated solid solution when at about room temperature is aged by heating for at least about 2 hours, e.g., about 5 to about 10 hours or 24 hours or longer, at about 500 C. to about 675 C. to effect precipitation of a fine and evenly dispersed vanadium compound in the matrix.

Vanadium serves as a precipitation hardening ingredient in the alloy of the invention and also provides additional beneficial results including solid solution strengthening, scavenging of impurities and grain refinement and also including elevation of the recrystallization temperature of the alloy when cold worked. The alloy of the invention must contain at least 0.7% vanadium in order to obtain satisfactory precipitation strengthening. Alloys without vanadium or with vanadium in solid solution do not have the vanadide precipitate which is characteristic of the precipitate strengthened alloy of the invention and which is required for obtaining improved strength. in accordance with the invention. The alloy of the invention contains no more than about 2% vanadium in order to avoid detrimental characteristics including formation of detrimental primary vanadides during solidification whereby hot and cold ductility would be reduced without benefit of increased strengths. Nickel in an amount of about 20% to about 40% is necessary in the alloy in order that the matrix thereof be characterized, at elevated temperatures, by solubility for vanadium sufficient to enable precipitation hardening in accordance with the invention. Small amounts of aluminum and/or silicon, e.g., about 0.1% to about 2% aluminum and/or about 0.1% to about 1% silicon, in accordance with the relationship /2 (percent Al)+percent Si=0.l% to 1% can be supplementary strengtheners in the alloy of the invention if properly balanced with vanadium. The alloy must not have a total amount of vanadium plus aluminum plus silicon greater than about 3% in order to avoid adverse efiects including reduced hot and cold ductility.

It is to be understood that the term balance essentially copper does not exclude small amounts of other elements which can be present as impurities without substantial detrimental effects or which can serve some useful purpose ancillary to the invention. Thus, an alloy in accordance with the invention can contain, in addition to ingredients specified in the composition, up to about 2% manganese, up to about 2% zinc, and/or magnesium, titanium, Zirconium and beryllium in amounts up to about 0.2% each and totalling not more than 0.5% as deoxidizers, malleabilizers, purifiers, etc., and can also contain incidental elements such as up to about 1% cobalt and up to about 1% tin. All percentages of composition herein are by weight. The elements lead, antimony, bismuth, sulfur, selenium, tellurium and phosphorus are especially detrimental impurities. Accordingly, the alloy should not contain more than about 0.005 each, or more than a total of about 0.01%, of lead, antimony and bismuth and should not contain more than about 0.002% each, or more than a total of about 0.005% of sulfur, selenium, telluriurn and phosphorus because these elements impair the good hot and cold workability of the alloy. Carbon must not exceed 0.1% inasmuch as greater amounts thereof would form carbides and thus tie up useful alloying additions. Iron in amounts up to about 5%, e.g., about 1.5% iron, is beneficial in the alloy of the invention in order to improve the resistance of the alloy to erosion by high-velocity seawater. The presence of about 5% iron is generally harmless in the alloy of the invention and it is to be understood that in all alloys in accordance with the invention the balance can include up to about 5% iron. In any event, the total amount of nickel, vanadium and copper in any alloy in accordance with the invention is at least about 92%.

In producing a precipitation hardened alloy in accordance with the invention, the alloy is first provided in a solid solution condition. The requisite solid solution condition can be obtained with a solution heat treatment whereby a copper-nickel-vanadium alloy of composition in accordance with the invention is heated for about 15 minutes to about 2 hours at about 850 C. to about 1100 C. and thereafter rapidly cooled, e.g., water quenched, from the solution treatment temperature. Where the vanadium content of the alloy is relatively high, e.g., about 1.5% to about 2%, the solution treatment temperature should also be relatively high, e.g., about 1000 C. to about 1100 C., if total solid solution is desired. The solid solution condition can also be obtained when the alloy is chill cast or otherwise quickly cooled after casting or when the alloy is cooled rapidly to room temperature after hot working, or even after rapid hot-warm working for a short period of time from a temperature of about 1050 C. to about 650 C. Full solution of vanadium is, of course, existent when the alloy is being hot worked at a high temperature, e.g., 1000 C. It is advantageous, in order to obtain good cold workability prior to precipitation by aging and to obtain especially good combinations of high yield and tensile strengths and ductility after aging, to provide the alloy in a fully solution heat treated condition such as is obtained by heating the alloy at about 1000 C. to about 1100 C. for at least about 15 minutes, e.g., about 30 minutes to about 60 minutes, or longer and thereafter water quenching the alloy. Solution treatment is also advantageous for dissolving some detrimental microstructural phases that may disadvantageously afiect the characteristics of the alloy.

The aging treatment is advantageously further controlled in relation to the vanadium content, supplementary hardeners, the solution heat treatment temperature and the amount of cold and/or warm work which has been accomplished, if any, as follows. Alloys with high percentages of precipitate forming additions such as vanadium, aluminum and silicon, if solution heat treated at high temperatures, e.g., 1100 C., can be aged at relatively high temperatures, e.g., 600 C., for 5 to 10 hours. If such alloys have been cold worked after solution treatment, the agin" temperature can be lowered by about 50 C. without requiring increased aging times. If the amount of precipitate forming additions in solid solution is relatively low, due either to low alloy content or low solution heat treatment temperatures, e.g., 850 C., or low warm working temperatures, e.g., 700 C., lower aging temperatures, e.g., 500 C. to 550 C., and longer aging times, e.g., 24 hours, are required.

in carrying the invention into practice, it is advantageous in order to produce, without cold working, precipitate strengthened copper-nickel-vanadium alloys characterized by high yield and ultimate tensile strengths of at least about 60,000 p.s.i. and 95,000 p.s.i., respectively, together with good tensile elongation of at least about 25%, that the copper-nickel-vanadium alloy be of a composition containing about 25% to about 35% nickel, 1% to 1.5% vanadium, up to about 0.5% aluminum, up to about 0.3% silicon with balance essentially copper. In obtaining the aforesaid high yield and tensile strengths of 60,000 p.s.i. and 95,000 p.s.i., respectively, the alloy is advantageously solution heat treated for about 30 minutes to about 60 minutes or longer at about 1025 C. to about 1075 C. and quickly cooled from this temperature, e.g., quenched in water, and is thereafter aged for about 5 hours to about 20 hours at about 575 C. to about 625 C. The method of cooling from the aging temperature is not critical and it is satisfactory to air cool the alloy after aging.

The alloy of the invention has good characteristics for cold working, including warm working, especially when in the solid solution condition and the yield and tensile strengths and hardness of the alloy either with or without aging treatment are substantially increased by cold working. For obtaining especially high yield and tensile strengths of at least 100,000 p.s.i. and 120,000 p.s.i., respectively, it is advantageous to cold work the alloy, e.g., at least about 30%, in the solution heat treated condition and thereafter age the alloy. Especially advantageous embodiments of the invention consist essentially of about 20% to about 40% nickel, 0.7% to about 1.5% vanadium, up to about 1% aluminum, up to about 0.5% silicon, with the sum of the silicon content plus onehalf the aluminum content not greater than 1% and with the total amount of vanadium plus aluminum plus silicon being 1.2% to 2% of the alloy, with balance essentially copper and are characterized by a hardness of at least 250 BHN, high yield and ultimate tensile strengths of at least about 125,000 p.s.i. and 130,000 p.s.i., respectively, along with satisfactory ductility when in the condition obtained by cold working at room. temperature to about 30% or more, e.g., 50%, 70% or even reduction in area and thereafter aging by heating at about 500 C. to about 600 C. for about 1 hour to about 24 hours.

The cold workability of a precipitation hardened alloy of the invention is dependent upon the amount of precipitate in the matrix and is relatively good when the degree of precipitation is relatively low and, thus, the ductility is relatively high. The process of cold working a fully or partially precipitation hardened alloy in accordance with the invention provides another method for obtaining a high strength alloy in accordance with the invention, particularly when high Work hardening rates are needed during cold working, e.g., in the production of spring wire.

For the purpose of giving those skilled in the art a better understanding of the invention and a better appreciation of the advantages of the invention, the following illustrative examples are given.

Chemical compositions of alloys 1 through 5, which are examples of the alloy composition of the invention, are set forth in Table I hereinafter.

TABLE I Alloy I V I Ni Si Al Fe Cu 1 Bal.=Balance including about 1.5% manganese and about 0.05% magnesium.

In producing alloys 1 through 5 appropriate amounts of electrolytic nickel and cathode copper were melted to- Where combinations of treatments set forth in Table II are referred to hereinafter, as in Table III, the treatments were performed in the sequence indicated, e.g.,

denotes the condition obtained by treating an alloy with treatment S followed by treatment CW and thereafter followed by treatment A5.5.

Results of tensile tests and hardness tests set forth in Table III illustrate the improved strength and hardness characteristics at room temperature of alloys in accordance with the invention and show that yield and ultimate tensile strengths of the order of 45,000 p.s.i. and 80,000 p.s.i. and greater, e.g., 60,000 p.s.i. and 100,000 p.s.i., respectively, combined with good tensile ductility, are readily achieved with alloys in accordance with the invention without cold working. It is to be further noted that the invention provides cold worked, precipitate strengthened alloys characterized by yield strengths of at least 100,000 p.s.i. and higher, and tensile strengths of at least 120,000 p.s.i. and higher and satisfactory ductility, e.g., at least about 5% tensile elongation, when in the condition obtained by cold working an alloy of the invention in the fully solution heat treated condition to reduce the cross sectional area thereof at least about 50%, e.g., 46% or 54%, and thereafter aging the alloy at 500 C. to 600 C. for 1 hour to 24 hours.

TABLE III Alloy Condition U.'1.S. Y.S. Elong. R.A. BHN

(p.s.i.) (p.s.i.) (percent) (percent) U.T.S. Ultimate Tensile Strength. Y.S.=Yield Strength at 0.2% ofiset.

Elong.=Elongation in l-inch gage length on 0.25 inch diameter gage section.

TAB LE II Condition Treatment Solution treated by heating at 1,050 C. for 30 minutes and water quenching. Aged by heating at 500 C. for 30 to 60 hrs. Aged by heating at 550 C. for 10 to 24 hrs. Aged by heating at 600 C. for 5 to 10 hrs. Cold worked to reduce cross sectional area about The cold working referred to in Table II and other tables hereinafter was accomplished by rolling at about room temperature, e.g., about 15 C. to about 100 C.

To further illustrate the advantages of the invention, a number of alloys, alloys A through D, not in accordance with the invention were prepared and compared with alloys within the contemplation of the invention. Chemical compositions of the alloys not in accordance with the invention are set forth in Table IV.

TABLE IV Alloy V Ni Si Fe 1 On 1 Mg Percent Percent Percent Percent Percent 30 0.2 0.1 Bal 0.005 30 0.2 0.7 Bal 30 0.2 0.1 lBal 0 05 30 0.2 0.1 Bal 0 05 1 Bal.=Balance including about 1.5% manganese.

The chemical composition of each of the alloys of Table IV is outside the range for vanadium required in alloys of the invention, i.e., 0.7% to 2% vanadium. Thus, alloys A and B were made without vanadium, alloy C has a vanadium content of 0.4%, which is too low to be in accordance with the invention, and the 4.8% vanadium content of alloy D is too high to be within the invention.

Results of room temperature tensile tests of alloys A, B and C and of hardness tests of alloys A through D are set forth in Table V and show inferior characteristics of the alloys not in accordance with the invention when in the conditions referred to in the table. The high vanadium content of alloy D was found to be severely detrimental to cold working characteristics inasmuch as the solution heat treated alloy cracked during the first pass when cold rolling was attempted. Microscopic examination of alloy D, when in the condition obtained by solution heat treatment in accordance with treatment S set forth hereinbefore, disclosed that the alloy contained large amounts of a brittle, primary nickel-vanadium compound embedded in the copper-nickel matrix. In contradistinction to alloy D, copper-nickel-vanadium alloys of compositions in accordance with the invention, e.g., alloy 3 of Table I, are characterized in the fully solution heat treated condition by a ductile, highly cold workable copper-nickel matrix which contains the vanadium in solid solution. Inasmuch as it is well understood in the art that 70:30 cupronickel alloys such as alloys A and B are not precipitation hardenable aging treatments were not applied to alloys A and B.

ing. The drawing also illustrates that cold worked alloys in accordance with the inventi n are characterized by improved retention of room temperature hardness and strength after being heated at elevated temperatures up to about 600 C.

The precipitation hardened alloy of the invention, including cold worked and aged embodiments thereof, is also characterized by retention of hardness with gOOd resistance against overagiug or embrittlernent when exposed to elevated temperatures for extended periods of time, e.g., 1000 hours or 2500 hours. Good stability of metallurgical characteristics of the alloys is illustrated by the following results of long-time exposure tests at an elevated temperature of 500 C. whereby specimens of alloy 3 in two precipitation strengthened conditions referred to hereinbefore as the S+A6 and S+CW50+A6 conditions were exposed at 500 C. for 2500 hours. The room temperature hardness of the solution treated and aged (without cold working) alloy was initially about 160 Brinell and was about 175 Brinell after 2500 hours exposure at 500 C. and, moreover, room temperature hardness tests after exposures of less than 2500 hours showed that the room temperature hardness of the alloy remained within a range of about 160 Brinell to about 175 Brinell throughout exposure for 2500 hours at 500 C. The room TABLE V Alloy Condition U.'I.S. Y.S. Elong. R.A. BHN

(p.s.i.) (p.s.i.) (percent) (percent) The heat treatment of alloy C was specially adjusted in accordance with the low vanadium content of the alloy in order to develop optimum strength characteristics but, even so, the strength of alloy C in conditions obtained by treatments S+A5 and S-l-CWSO-l-AS was found substantially inferior to precipitate strengthened alloys in accordance with the invention.

In the accompanying drawing, characteristics of the alloy of the invention are further illustrated and compared with characteristics of an alloy having less vanadium than is required for the alloy of the invention. Referring now to the drawing, it is noted that the curves pertaining to alloys 3, 4 and C were constructed by plotting the room temperature hardnesses of the alloys after aging the alloys by heating for about 4 hours at the temperatures indicated in the drawing and, thereafter, correlating the plotted points by means of the curves in the drawing. Prior to aging, the alloys referred to in the drawing were in the condition obtained by solution heat treating at about 1050 C. for minutes, quenching and thereafter cold working at room temperature to about reduction in area. It is clearly apparent from the drawing, taken in conjunction with the foregoing tables, that the room temperature hardness and strength of alloys 3 and 4, containing 0.83% vanadium and 1.33% vana dium, respectively, are substantially increased by heating at temperatures of about 400 C. to about 650 C. when in the cold worked condition, whereas no substantial or commercially worthwhile enhancement in qualities of hardness or strength is obtained by aging the similarly cold worked alloy C, which contains only 0.4% vanadium, at any of the temperatures referred to in the drawtemperature Brinell hardness of the solution heat treated, 50% cold Worked and aged alloy was initially about 225 Brinell and was Within a range of about 230 Brinell to about 250 Brinell during and after exposure at 500 C. for periods up to 2500 hours.

Very good combinations of high strength and ductility can be obtained by warm working the alloy of the invention at an elevated temperature below the recrystallization temperature of the alloy, e.g., by warm working at 550 C. to about 750 C. immediately following hot working. Warm working at temperatures within the range of rapid precipitation, e.g., about 550 C. to about 650 C., accelerates precipitation and accordingly, precipitation strengthening can be accomplished, at least in part, during warm working. An especially advantageous process provided by the invention, both from the viewpoint of obtaining an especially good combination of high strength and good ductility and also of obtaining expediency and economy in production, is to hot-warm work the alloy by hot working, e.g., hot rolling or hot forging, the alloy and continuing to work the alloy while the temperature thereof decreases to within the temperature range of rapid precipitation. For example, an advantageous hotwarm working process comprises providing the alloy in a solid solution condition at about 1050 C. to about 1075 C., commencing to hot work the alloy while within this temperature range and continuing to work the alloy as the temperature thereof decreases to about 650 C. with control of the working steps to provide that the cross-section of the alloy is reduced at least about 65% by warm working while the alloy is in an advantageous, warm working temperature range of about 750 C. to

about 650 C. Where the alloy is not fully aged during warm working the alloy can be further strengthened by additional aging treatment or by room temperature cold working, e.g., cold working at least about 30%, and additional aging treatment in accordance with the invenion. Test results illustrating room temperature tensile characteristics of the alloy of the invention and of an alloy not within the invention in hot-warm worked conditions with and without room temperature working and/or ad ditional aging treatment are set forth in Table VI. The results in Table VI pertain to alloys which were hot-warm worked by starting with hot forging the ingots at about 1050 C. and, then, continuing with the working operations by forging and rolling until finishing working at about 650 C. to 750 C. The condition thus obtained is identified in Table VI as Condition R. The numbers following CW in Table VI show the percent reduction in area accomplished by room temperature cold working after hot-warm Working and the other condition designations in this table are to be understood as referred to in Table II and in the next paragraph subsequent thereto.

Additional desirable characteristics possessed by the alloy of the invention include notch ductility, welda'bility and corrosion resistance, including resistance to stresscorrosion cracking. The ratios of notch tensile strength (with a notch stress concentration factor, K greater than 10) to ultimate tensile strength of alloys 1, 2, 3, 4

TABLE VI Alloy Condition U.T.S. Y.S Elong. RA. BI-IN (p.s.i.) (p.s.i (percent) (percent) Improved strength characteristics of the precipitate strengthened alloy of the invention when at elevated temperatures of 300 C. and 400 C. are further illustrated by test results set forth in Tables VII and VIII. The results set forth in Table VII were obtained by tensile testing the alloys 1, 2, 4 and 5 at 300 C. when these alloys were in the precipitation strengthened condition obtained 'by solution treating at 1050" C. for /2 hour followed by water quenching and thereafter aging at 600 C. for five to ten hours. Also included in Table VII are results of tensile testing alloy B at 300 C. when in condition S.

Test results set forth in Table VIII illustrate elevated temperature characteristics of alloy 3 when in conditions obtained by solution heat treatment with and Without aging and/or cold Working to 43% reduction in area (CW43).

and 5 in the conditions S and SJ-l-A6, when tested at room temperature, ranged from 1.24 to 1.60. For example, the notch tensile strength of alloy 2 was 128,300 p.s.i. when tested in a precipitation strengthened condition having a smooth bar ultimate tensile strength of 103,800 psi. and thus the alloy had a notch tensile strength/ ultimate tensile strength ratio of 1.24. In stress-corrosion tests, U-bend specimens of alloy 3 in the four conditions referred to in Table III hereinbefore, namely, conditions S, S+A6, S+CW50 and Si+'CW50+A6, were suspended above an aqueous concentrated ammonia solution at room temperature. The ammonia solution was renewed daily and the specimens were examined daily for detection of pitting, cracks, discoloration and general corrosion attack for 50 days. Throughout the 50-day test, the stress-corrosion resistance of all the specimens of alloy 3 in ammonia-air-water vapor was at least equal to the corrosion resistance of similarly tested specimens of a 70:30 cupronickel alloy without vanadium (alloy B of Table IV) and no cracking occurred in any of the tested specimens of alloy 3. In contrast to the good stress-corrosion resistance exhibited by copper-nickel alloys 3 and B, a 65% copper- 25% zinc-brass alloy in the annealed and 50% cold worked condition cracked in 2.2 hours when subjected to the same aforementioned stress-corrosion test applied to copper-nickel alloys 3 and B.

The present invention is particularly applicable to the production of precipitation hardenable cupronickel alloy products and articles and to production. of precipitate strengthened cupronickel alloy products and articles, in-

eluding cold worked and precipitation hardened products and articles, which articles and products include plate, sheet, bar, wire, tubing, piping, forgings, press forgings, springs and cold-head parts. The invention is also applicable to the production of precipitation hardenable cupronickel alloy castings and precipitate strengthened cupronickel alloy castings, e.g., pump impellers.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be Within the purview and scope of the invention and appended claims.

I claim:

1. A precipitate strengthened copper-nickel-vanadium alloy consisting essentially of about to about 40% nickel, at least 0.7% to about 2% vanadium, up to about 1% silicon and up to about 2% aluminum. in proportions such that the sum of the percent silicon plus /2 the percent aluminum is not greater than 1% of the alloy and the sum of the percent silicon plus the percent aluminum plus the percent vanadium is not greater than 3% of the alloy with balance essentially copper and having a microstructure comprising a face-centered-cubic copper-nickel matrix with a precipitate of a vanadium compound finely and evenly dispersed in said matrix.

2. A precipitate strengthened copper-nickel-vanadium alloy consisting essentially of about to about nickel, at least 1% to about 1.5% vanadium, up to about 0.3% silicon, up to about 0.5% aluminum with balance essentially copper and having a microstructure comprising a face-centered-cubic copper-nickel matrix with a precipitate of a vanadium compound finely and evenly dispersed in said matrix, said precipitate strengthened alloy being characterized by a yield strength of at least 60,000

3. A cold worked precipitate strengthened coppernickel-vanadium alloy consisting essentially of about 20% to about nickel, at least 0.7% to about 1.5% vanadium, up to about 0.5% silicon and up to about 1% aluminum in proportions such that the sum of the percent silicon plus the percent aluminum plus the percent vanadium is 1.2% to 2% of the alloy with balance essentially copper and having a microstructure comprising a facecentered-cubic copper-nickel matrix with a precipitate of a vanadium compound finely and evenly dispersed in said matrix, said alloy being characterized in the cold worked and precipitate strengthened condition by a yield strength of at least about 120,000 p.s.i.

4. A process for producing a precipitate strengthened copper-nickel-vanadium alloy comprising providing an alloy consisting essentially of about 20% to about 40% nickel, at least 0.7% to about 2% vanadium, up to about 1% silicon and up to about 2% aluminum in proportions such that the sum of the percent silicon plus /2 the percent aluminum is not greater than 1% of the alloy and the sum of the percent silicon plus the percent aluminum plus the percent vanadium is not greater than 3% of the 12 alloy with the balance essentially copper in a solid solution condition and age hardening said alloy by heating the alloy at a temperature of about 500 C. to about 675 C. for at least about 2 hours to effect precipitation of a vanadide precipitate therein.

5. A process as set forth in claim 4 wherein the coppernickel-vanadium alloy is cold worked while in the solid solution condition prior to aging.

6. A process as set forth in claim 4 wherein the coppernickel-vanadium alloy contains silicon or aluminum in an amount of at least 0.1%.

7. A process as set forth in claim 4 wherein the coppernickel-vanadium alloy is warm worked at about 550 C. to about 750 C. prior to aging.

8. A process for producing a hot-warm worked, precipitate strengthened copper-nickel-vanadium alloy comprising providing an alloy consisting essentially of about 20% to about 40% nickel, at least 0.7% to about 2% vanadium, up to about 1% silicon and up to about 2% aluminum in proportions such that the sum of the percent silicon plus /2 the percent aluminum is not greater than 1% of the alloy and the sum of the percent silicon plus the percent aluminum plus the percent vanadium is not greater than 3% of the alloy with balance essentially copper in a solid solution condition at a temperature of at least about 1050 C., hot working the alloy at a temperature of at least 1050 C., continuing to work the alloy as the temperature thereof decreases to about 750 C. and further continuing to work the alloy to reduce the cross section thereof at least about and effect precipitation of a vanadium compound therein while the temperature of the alloy is decreasing from about 750 C. to about 650 C.

9. A process as set forth in claim 8 wherein the coppernickel-vanadium alloy is aged at least about 2 hours at about 500 C. to about 675 C. after being worked at about 650 C. to about 750 C.

10. A process as set forth in claim 8 wherein the coppernickel-vanadium alloy is cold worked at room temperature to reduce the cross section thereof at least about 30% after being worked at about 650 C. to about 750 C. and is aged at least about 2 hours at 500 C. to about 675 C. after being cold Worked.

References Cited OTHER REFERENCES Hansen: Constitution of Binary Alloys, McGraW-Hill Book Co., New York, N.Y., 1958, pp. 1055-4057.

CHARLES N. LOVELL, Primary Examiner. 

8. A PROCESS FOR PRODUCING A HOT-WARM WORKED, PRECIPITATE STRENGTHENED COPPER-NICKEL-VANADIUM ALLOY COMPRISING PROVIDING AN ALLOY CONSISTING ESSENTIALLY OF ABOUT 20% TO ABOUT 40% NICKEL, AT LEAST 0.7% TO ABOUT 2% VANADIUM, UP TO ABOUT 1% SILICON AND UP TO ABOUT 2% ALUMINUM IN PROPORTIONS SUCH THAT THE SUM OF THE PERCENT SILICON PLUS 1/2 THE PERCENT ALUMINUM IS NOT GREATER THAN 1% OF THE ALLOY AND THE SUM OF THE PERCENT SILICON PLUS THE PERCENT ALUMINUM PLUS THE PERCENT VANADIUM IS NOT GREATER THAN 3% OF THE ALLOY WITH BALANCE ESSENTIALLY COPPER IN A SOLID SOLUTION CONDITION AT A TEMPERATURE OF AT LEAST ABOUT 1050*C., HOT WORKING THE ALLOY AT A TEMPERATURE OF AT LEAST 1050*C., CONTINUING TO WORK THE ALLOY AS THE TEMPERATURE THEREOF DECREASES TO ABOUT 750*C. AND FURTHER CONTINUING TO WORK THE ALLOY TO REDUCE THE CROSS SECTION THEREOF AT LEAST ABOUT 65% AND EFFECT PRECIPITATION OF A VANADIUM COMPOUND THEREIN WHILE THE TEMPERATURE OF THE ALLOY IS DECREASING FROM ABOUT 750*C. TO ABOUT 650*C. 